1. Field of the Invention
The invention is related generally to the field of electronic devices, and more particularly, to current aperture vertical electron transistors (CAVETs) with ammonia (NH3) molecular beam epitaxy (MBE) grown p-type Gallium Nitride (GaN) as a current blocking layer (CBL).
2. Description of the Related Art
(Note: This application references a number of different publications as indicated throughout the specification by one or more reference numbers within brackets, e.g., [x]. A list of these different publications ordered according to these reference numbers can be found below in the section entitled “References.” Each of these publications is incorporated by reference herein.)
FIG. 1 is a schematic illustration of a CAVET 100, including higher/heavily n-type doped Gallium Nitride (n+-GaN) 102, lower or lightly n-type doped GaN (n−-GaN) 104, aperture 106, Current Blocking Layer (CBL), unintentionally doped (UID) GaN 108, aluminum gallium nitride (AlGaN) 110, source 112, gate 114, and drain 116. The CAVET 100 is a vertical device comprised of an n-type doped drift region 118 to hold voltage and a horizontal two-dimensional electron gas (2DEG) 120 to carry current flowing from the source 112, under a planar gate 114, and then in a vertical direction to the drain 116 through an aperture 106.
As shown in FIG. 1, electrons flow horizontally from the source 112 through the 2DEG (dashed lines 120), and then vertically through the aperture region 106 to the drain 116, and are modulated by the gate 114. A fundamental part of a CAVET is the CBL, which blocks the flow of the current and causes on-state current to flow through the aperture 106.
Previously, the CBL has been fabricated by ion implantation. For example, two prior art designs of a CBL in a CAVET are described below:
1. AlGaN/GaN CAVETs with Aluminum (Al) ion implanted GaN as the CBL [1]; and
2. AlGaN/GaN CAVETs with Magnesium (Mg) ion implanted GaN as the CBL [2].
In both prior art designs, functioning devices have been achieved by successfully blocking the current from flowing through the CBL region by the use of an ion-implanted GaN layer as a CBL region. The damaged (trap-filled) CBL region introduced a barrier to the electrons injected from the source, thereby preventing the electrons from flowing directly into the drain without passing under the gate.
Nonetheless, there is a need in the art for improvements in CAVET designs. The present invention satisfies that need.